*{
    padding: 0;
    margin: 0;
}
.float-left{
    float: left;
}
.float-right{
    float: right;
}
.clearfix:after,
.clearfix:before{
    content: "";
    display: block;
    clear: both;
}
.top{
    width: 300px;
    margin: auto;
}
img{
    width: 300px;
    height: 300px;
    text-align: center;
}
h1,h2,h3,h5,p{
    text-align: center;
}
.jianjie-inner{
    width: 80%;
    margin: auto;
}
.jianjie{
    border: 3px solid silver;
    border-radius: 20px;
    margin-top: 100px;
    width: 42%;
    padding: 10px;
}
h4{
    font-size: 25px;
}
h5,p{
    font-size: 30px;
}
footer{
    margin: 100px;
    border:solid 5px slategrey;
    border-radius: 20px;
}